Various types of depilatory apparatus are known in the art. One type of manually operated device, exemplified in U.S. Pat. Nos. 2,458,911, 2,486,616 and 1,743,590 and Swiss Patent 268,696, employs a coil spring which engages hairs in spaces between the convolutions thereof and pulls the hair away from the skin as the spaces between the convolutions are closed. The operation of this type of device is highly inefficient, slow and painful.
Early power driven depilatory devices are exemplified in U.S. Pat. No. 4,079,741 of present Applicants. U.S. Pat. No. 4,079,741 describes a hair removal device employing an axially disposed helical spring which is simultaneously driven in axial rotation by an electric motor and reciprocatingly compressed and extended by a cam operated by the electric motor. This apparatus is relatively complex and costly and has not reached the market.
A highly successful power driven depilatory device is described in Applicant's U.S. Pat. No. 4,524,772 which shows an electrically powered depilatory device including a hand-held portable housing, motor apparatus disposed in the housing and a helical spring comprising a plurality of adjacent windings arranged to be driven by the motor apparatus in rotational sliding motion relative to skin bearing hair to be removed, the helical spring including an arcuate hair engaging portion arranged to define a convex side corresponding thereto whereat the windings are spread apart and a concave side corresponding thereto whereat the windings are pressed together, the rotational motion of the helical spring producing continuous motion of the winding from a spread-apart orientation at the convex side to a pressed together orientation at the concave side and for engagement and plucking of hair from the skin, whereby the surface velocities of the windings relative to the hair greatly exceed the surface velocity of the housing relative thereto.